Old Scourge Loses Ground In West Africa

By JAMES BROOKE, Special to the New York Times

Published: September 3, 1987

SAMANDEMI, Burkina Faso—
In the dusty mud brick villages around here, the medieval sight of a small child leading blind men linked by poles is becoming increasingly rare.

For centuries, farmers here thought it was their destiny to go blind by middle age.

More recently, scientists penetrating this remote part of West Africa discovered a link between what villagers called ''poor man's disease'' and microscopic parasites carried by river-bred flies.

The reaction in villages like this one, where up to 20 percent of adult men were blind, was to abandon wide swaths of fertile land along riverbanks.

Now onchocerciasis, or river blindness, appears to be under control.

''Today over 90 percent of the program area is under control and the riverine area is safe for resettlement,'' said Ebrahim M. Samba, director of the Onchocerciasis Control Program, which is administered by the World Health Organization in Ouagadougou, the capital. ''Over three million children born in the last decade are fully protected from becoming blind.''

In Burkina Faso, the former Upper Volta, the West African nation hit hardest by the disease, the new mastery of the disease commonly known as ''oncho'' is changing the landscape. In a land rush, peasants have returned an estimated 1,000 square miles of fertile farmland to cultivation. Abandoned villages are being repopulated, and food production is climbing.

Worldwide, varying stages of ''oncho'' affect an estimated 20 to 30 million people - in southern Mexico, the Pacific coastal regions of Guatemala, Colombia and Ecuador, the Orinoco river basin in Venezuela and Brazil, in Southern Yemen and in Africa from Senegal to Ethiopia.

While malaria spreads largely unchecked through Africa, the successful ''oncho'' campaign involving helicopters, larvacides and extensive laboratory research may serve as an example for other health campaigns in the third world, scientists say.

Since it was begun in 1974, the program has lifted the threat of river blindness from a core area comprising Benin, Burkina Faso, Ghana, Ivory Coast, Mali, Niger and Togo. Last year, the program was expanded to Guinea, Guinea Bissau, Senegal and Sierra Leone.

In this village, southwest of Bobo Dioulasso, the country's second-largest city, and half a mile from the River Kou, river blindness is largely an unhappy memory.

''There are very few blind people here now,'' Adama Sanon, Samandemi's village chief, said recently.

The infection is borne by a black fly, aptly called Simulium damnosum. The fly's ''damnable'' nature came from its sting and its invisible cargo - larvae.

In the human body, these larvae develop into threadlike worms. Lumped in nodules, the worms cause an itching so severe that ''oncho'' is one of only a handful of diseases that have been known to drive Africans to suicide.

Moving through the body, the worms invade the eye. The buildup of dead worms in the eye eventually causes lesions and blindness.

A new drug, ivermectin, is now undergoing field trials in Burkina Faso and appears to reverse the condition without adverse side effects. But, without controlling the carrier, medication cannot stop new infections.

Since the black fly was the sole carrier and the worms had an estimated life of 15 to 18 years, scientists reasoned that the disease could be controlled if they could wipe out most of the flies for a 20-year period.

In a program that has cost $200 million to date, a fleet of aircraft have flown weekly missions during the rainy season, spraying 11,000 miles of West African rivers with larvacides approved by independent ecologists. The fly fought back. New, resistant strains emerged and had to be countered with different larvacides. Winds, blowing across Africa from east to west, brought new flies into previously cleared areas. Scientists discovered that flies can travel 400 miles in a day on the wind.

To stop reinvasion, the Oncho Program last year was expanded east, from a core area of 295,000 square miles to one of 502,000 square miles.

While scientists do not talk of eradication, they believe that the problem now is sufficiently under control to start turning over monitoring responsibility to local authorities.

''In 90 percent of the program area, the transmission of onchocerciasis has been interrupted,'' read a report prepared last year by the United States Agency for International Development. ''An estimated 27,000 cases of blindness have been prevented in Burkina Faso alone over the past decade.''

Map shows area in which threat of river blindness has been lifted (NYT) (Pg. A11)